A sol formed from an inorganic material dispersed in an organic solvent has good processability and storability. Silica and metal oxides are typical inorganic materials used for dispersal in an organic solvent. In particular, the silica has advantages such as being cheap, high hardness, a low thermal expansion coefficient or the likes. An organic/inorganic composite material which has both advantages of the inorganic material and the organic material is formed from a mixture of an organic polymer and a sol. Specifically, the organic/inorganic composite material may have a high content of inorganic materials by using a high concentration sol formed from silica type materials.
The different shapes of silica particles, such as a spherical shape, elongated shape or platelet, have different reactivities and are formed from various types of silica aqueous or alcohol dispersion with different processes. Nissan Chemical discloses an elongated shape silica dispersion, for example, referring to U.S. Pat. No. 5,221,497 and U.S. Pat. No. 5,597,212. Also, U.S. Pat. No. 5,902,226 discloses a spherical shape silica. However, the organic dispersion or sol, or even the aqueous dispersion or sol, of the silica platelets, has never been commercially available as spherical or elongated shape silica particles.
Only few references relevantly disclose the silica platelets. For example, U.S. Pat. No. 5,796,177 discloses a method for forming the silica platelets, in which the silica source is mixed with NaOH repeatedly and then thoroughly mixed with Al2O3 or ZrO2 in a high temperature to form the silica platelets. However, the sol of the silica platelets is milk white and opaque. In addition, the silica platelets can only be dispersed in water, and cannot form an organic sol. Moreover, the step of adding NaOH repeatedly reduces process stability.
Silica platelets have a larger surface area than spherical and elongated shape silica particles and its size is also easier to control. Thus, the silica platelets have better applicability. A novel organic dispersion of inorganic platelets is needed to be developed.